Mechanical wrenches and screw, bolt or other connector drivers have been in use for many years. Likewise, the problem of mechanical drive tools stripping or breaking driven connectors or applying improper or undesired levels of connection torque or force has been long-felt in the arts of construction and mechanical engineering, and probably dates from the earliest wrenches.
Torque wrenches have been available for many years and, generally speaking, allow a user to pre-set an amount of levered force (torque) as a maximum to be applied to a bolt connector/fastener being tightened by the wrench. Beyond that preset amount of torque, the torque wrench driver will mechanically slip from the wrench handle, rotating more freely with respect to it, and therefore without applying a higher torque.
In addition, a wide variety of remediation techniques have been suggested or attempted to address the problem of connector heads, threads or other parts stripping or breaking due to driving, or due to stress or strain after driving. Typically, “How to” guides, such as those found on eHow.com, provide a variety of potential solutions for extracting stripped screws, bolts or other connectors, ranging from jury-rig solutions such as cutting a new notch into a stripped screw head for new traction, to complex equipment and approaches such as extractors or welding ancillary bolts onto a stripped bolt. See, e.g., eHow, How to Remove Stripped Screws and Bolts, available on the Internet at eHow.com, accessed on Apr. 1, 2012.
The type of stripping or other damage that may occur from overdriving a connector varies by driver tip type. Phillips head screwdrivers are designed to “cam out” beyond an amount of torque that varies based on the exact connection head and driver tip type and on the pressure applied into those heads. In this way, the threads of Phillips screws and holes in a connected material into which they are driven are often spared from stripping, but continued rotation of the driver against the head, after camming-out, typically strips the screw head. Robertson screwdrivers and heads, by contrast, resist camming out, but create a greater risk of thread and hole stripping.
With almost any driver tip, provided that enough torque and pressure are applied against a strong enough connector head and hole, a more radical connection driving failure can happen, such as the screw shearing or otherwise breaking off into pieces, or bending. Removing stripped connectors can be very difficult and expensive, involving collateral damage and specialized extraction tools. And removing sheared or broken connectors can be even more difficult and expensive due to difficulties in grabbing a buried part of the connector that has broken off inside a connected element.